[aembleton]

You get given water during races, and you don't need a support team for that to happen. There are people handing them out at set locations, so there's no need to carry all of that with you. You often get gels too and its worth training with that brand that they are giving out so that your gut is ready for it, but you can't rely on them because they do sometimes run out.

I've never seen them run out of water though, and it would be a lot to carry for a marathon.